High-performance structured packing for a fluid contacting column

ABSTRACT

The packing consists of a pile of plates comprising corrugations forming a succession of positive and negative edges, each edge comprising fins, each fin being made up of at least one band cut out in one of the plates and remaining secured to the plate on at least one side, the band being deformed so as to create an orifice forming a discontinuity on the surface of the plate, wherein the direction of the edges of a plate forms a non-zero angle with respect to the direction of the edges of an adjacent plate. Each plate comprises at least one longitudinal zone parallel to one lip of the plate where the edges comprise no orifice, the zones being positioned in such a way that two adjacent plates have their zone one above the other so as to form at least one point of contact between a positive edge and a negative edge of the two adjacent plates.

FIELD OF THE INVENTION

The present invention relates to the sphere of fluid contactingequipments.

The purpose of contacting columns is to provide contact between fluidsin order to achieve material or heat transfers between the fluids. Thistype of fluid contacting equipment is widely used to carry outdistillation, rectification, absorption, heat exchange, extraction,chemical reaction operations, etc.

BACKGROUND OF THE INVENTION

Contacting columns generally consist of a cylindrical enclosure providedwith internal contacting elements promoting exchange between the fluids.In the column, the fluids can circulate in a cocurrent or acountercurrent flow. In general, the column allows to provide intimatecontact between an ascending gas phase and a descending liquid phase.The contacting elements that increase the contact surface between thefluids can be trays, structured packings, i.e. the juxtaposition ofseveral unitary elements, identical or not, arranged in an orderedmanner, corrugated sheets for example, or random packings, i.e. anarchicpiles of unitary elements, for example rings, spirals.

Structured packings can consist of folded sheets arranged in anorganized manner as big blocks, as described for example in documentsU.S. Pat. No. 3,679,537 and U.S. Pat. No. 4,296,050. The new generationof random packings generally consists of metal elements provided withperforations and arc portions with sophisticated shapes.

Structured packings afford the advantage of providing a large geometricarea for a given representative diameter, generally the hydraulicdiameter of the channels, however the effective area is less than orclose to the geometric area thereof. A contrario, random packingsprovide rather low geometric area values in relation to thecharacteristic size thereof, but they can have effective transfer areasgreater than the geometric areas thereof.

Patent application US-2010/0,213,625 describes a packing combining theadvantages of structured packings and the advantages of random packings.Such a structured packing is so designed as to exhibit thecharacteristics of random packings inducing in particular liquiddetachment from the surface of the packing and allowing to develop aneffective area substantially greater than the geometric area thereof.This packing (FIG. 1) consists of a pile of plates (FIGS. 2, 3A and 3B)comprising corrugations, each plate being inscribed between two parallelplanes, the distance between said planes ranging between 5 and 50 mm.The corrugations form a succession of positive (top of a channel, CA2)and negative (hollow of a channel, CA1) edges comprising fins inscribedbetween said two parallel planes. The fins are formed by cutting anddeforming a band B. Notches C1 and C2 are cut out in band B. Notches C1and C2 form an angle of 90° to the principal direction of the channels.Bands B remains secured to the plate at ends E1 and E2. Band B isdeformed so as to follow a triangular shape substantially symmetrical tothe initial shape thereof, in relation to the meridian plane P. Thewidth L of a band B is approximately equal to the distance between twocontiguous bands along a channel (between 1 and 15 mm). Direction (D) ofthe edges of a plate forms a non-zero angle to the direction (D′) of theedges of an adjacent plate. The positions of two consecutive plates aresuch that the principal directions of the edges of each one of the twoplates range from 60° to 90°, two consecutive plates being mountedopposite each other.

FIG. 4 and FIG. 5 respectively show two possible contacts between twoconsecutive plates. A contact between two plates is referred to as goodwhen it occurs between a positive edge of a plate and a negative edge ofan adjacent plate. In FIG. 4, there is a match between two opening-freezones and a good contact between the plates so that there is nointerpenetration risk. In FIG. 5, there is a match between, on the onehand, an opening-free zone (lower plate) and a zone provided with anopening (upper plate); there is thus no good contact between the platesso that they can interpenetrate, therefore no satisfactory setup ispossible with an embodiment compatible with an industrial production.

The likelihood of bad contacts is illustrated in FIG. 6. This figurecorresponds to a 2D view of two superimposed plates. It can be notedthat, despite some zones with good contacts (circles in dotted line),there is a large number of bad contacts (circles in solid line). Whenmounting industrial packing blocks, the many plates making up a blockare tightly held against one another and not having enough contactpoints results in failure to respect the total block ; there are zoneswith entangled plates harmful to the flow and other zones with too greata spacing, with possible gas or liquid bypass.

In order to maintain the packing performances, it is essential toprovide good mounting of the plates in relation to one another, i.e.tangle-free mounting.

The object of the invention thus relates to a packing combining theadvantages of structured packings and the advantages of random packings,such as the packing described in document US-2010/0,213,625, wherein thenumber of good contacts is maximized by means of at least onelongitudinal zone parallel to one lip of the plate where the edgescomprise no orifice.

SUMMARY OF THE INVENTION

In general terms, the invention relates to a structured packing of afluid contacting column defining an exchange surface for at least oneliquid phase intended to come into intimate contact with at least onegas phase, said packing consisting of a pile of plates comprisingcorrugations, each plate being inscribed between two parallel planes(L1; L2), said corrugations forming a succession of positive andnegative edges, each edge comprising fins (A) inscribed between said twoparallel planes, each one of said fins consisting of at least one band(B) cut out in one of said plates, width (L) of the band ranging between1 and 15 mm, the band remaining secured to the plate on at least oneside (E1; E2) and the band being deformed so as to create an orificeforming a discontinuity on the surface of the plate, wherein direction(D) of the edges of a plate forms a non-zero angle with respect todirection (D′) of the edges of an adjacent plate. According to theinvention, each plate comprises at least one longitudinal zone parallelto one lip of the plate, where the edges comprise no orifice, said zonesbeing positioned in such a way that two adjacent plates have their saidzone one above the other so as to form at least one point of contactbetween a positive edge and a negative edge of two adjacent plates.

According to the invention, each plate can comprise at least one zone atthe centre of the plate and/or on the periphery of the plate. Accordingto one embodiment, each plate comprises a zone at the centre of theplate and a zone close to the lip.

According to the invention, each longitudinal zone can extend over theentire length of the lip of the plate it is parallel to.

According to the invention, the width of a longitudinal zone can begreater than or equal to width (E1, E2) of the bands of the fins.

The invention also relates to a fluid contacting column comprisingseveral blocks with structured packings according to the invention,wherein said direction of the packing channels is oriented at an angleranging between 10° and 75° with respect to the axis of the column andwhere the median planes of the structured packing of one of said blocksform an angle ranging between 20° and 90° with respect to the medianplanes of the adjacent blocks.

The invention furthermore relates to an application of a contactingcolumn according to the invention for gas drying, natural gasdeacidizing, fumes decarbonation, Claus tail gas treatment ordistillation.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the invention will be clear fromreading the description hereafter, with reference to the accompanyingfigures wherein:

FIG. 1 shows a packing made up of a pile of corrugated plates comprisingfins,

FIG. 2 diagrammatically shows a corrugated plate form without fins,

FIGS. 3A and 3B show a band cut out in a channel of a corrugated plate,

FIG. 4 shows a case of good contact between two consecutive plates,

FIG. 5 shows a case of bad contact between two consecutive plates,

FIG. 6 illustrates the likelihood of bad contacts and good contactsbetween two consecutive plates,

FIG. 7 illustrates a packing plate with three opening-free zones, and

FIG. 8 shows a case with two packing plates with three opening-freezones highlighting points of good contact (dotted lines).

DETAILED DESCRIPTION

FIGS. 2, 3A and 3B show a rectangular corrugated sheet or plate formingthe base of the structured packing according to the invention. Thecorrugations are bounded by two parallel planes L1 and L2 that arerelatively close. Distance h between L1 and L2 can range between 5 mmand 50 mm, it is preferably greater than 10 mm, and it preferably rangesbetween 10 mm and 30 mm. Meridian plane P divides the space between L1and L2 into two equal parts. In FIGS. 2, 3A and 3B, the corrugationshave a triangular shape and they are distributed on either side ofmeridian plane P: part of the corrugations is positioned on one side ofplane P and the other part is positioned on the other side of plane P.The corrugations form a succession of channels extending in thedirection shown by arrow D. In FIG. 2, channel CA1 is beneath plane P.Channel CA2 contiguous to channel CA1 is above plane P. Corrugationsgenerating channels that touch planes L1 and L2 without exceeding thespace delimited by these two planes are preferably selected. Thus, thecorrugated sheets occupy a maximum surface area in the plane sectiondefined by planes L1 and L2. A channel comprises either a positive edge(CA2) or a negative edge (CA1).

Various plate corrugation shapes can be used for a structured packingaccording to the invention. For example, sinusoidally corrugated platescan be employed. It is also possible to use corrugations that are notsymmetrical, for example a sequence of semi-circles and triangles.Plates comprising irregular and random corrugations can also beutilized.

The corrugations that form a succession of positive (top of a channel)and negative (hollow of a channel) edges comprise fins inscribed betweenthe two parallel planes. Each fin consists of at least one band cut outin one of the plates, the width of the band ranging between 1 mm and 15mm, the band remaining secured to the plate on at least one side and theband being deformed so as to create an orifice forming a discontinuityon the surface of the plate. Direction (D) of the edges of a plate formsa non-zero angle with respect to direction (D′) of the edges of anadjacent plate.

The positions of two consecutive plates are such that the principaldirections of the edges of each one of the two plates range between 60°and 90°.

In order to improve the performances of this type of packing, it isessential to provide good mounting of the plates, i.e. without thembeing entangled. The plates are therefore modified so as to maximize thenumber of good contacts between two plates, i.e. contacts occurringbetween a positive edge of a plate and a negative edge of an adjacentplate.

According to the invention, each plate comprises at least onelongitudinal zone parallel to one lip of the plate where the edgescomprise no orifice. These zones are positioned in the structuredpacking in such a way that two adjacent plates have their zone one abovethe other so as to form at least one point of contact between a positiveedge and a negative edge of two adjacent plates.

Preferably, each longitudinal zone extends over the entire length of thelip of the plate it is parallel to. The width of a longitudinal zone isgreater than or equal to the width (E1, E2) of the bands of the fins.

The diagram of FIG. 7 is a front view of a corrugated plate of height Hand length L. Height H is the height of the packing blocks, it isgenerally close to 20 cm but it can range between 2 cm and 1 m,preferably between 10 cm and 30 cm. Length L is variable and it dependson the diameter of the column containing the packing, this diametertypically ranging from 5 cm to 15 m. For conventional industrialcolumns, i.e.

with a diameter above 1 m, the lengths preferably range between 0.5 and3 m, more preferably between 1 and 2 m. The plate of FIG. 7 is providedwith three opening-free zones A, B and C. These zones follow thedirection perpendicular to the height of the plates.

FIG. 8 corresponds to the case of FIG. 6, but it uses the presentinvention with three opening-free zones. It can be observed here thatthe proportion of good contacts is much greater than in the prior case,increasing from 25% good contacts to 33%, and the plate length withoutgood contact is reduced by a factor of two.

The corrugated sheets provided with fins are piled so as to form astructured packing. Preferably, the direction of the channels of acorrugated sheet is offset in relation to the direction of the channelsof the adjacent sheets, for example by an angle ranging between 20° and90°, preferably by an angle having a value substantially close to 90°.

The packing according to the invention can be used for gas drying,natural gas deacidizing, fumes decarbonation and Claus tail gastreatment. In these applications, the gas to be treated is contactedwith a liquid absorbent solution in a contacting column. This columncomprises several blocks containing structured packings according to theinvention, wherein the direction of the channels of the packings isoriented at an angle ranging between 10° and 75° with respect to theaxis of the column and wherein the median planes of the structuredpacking of one of said blocks form an angle ranging between 20° and 90°with respect to the median planes of the adjacent blocks.

The packing according to the invention can be used for distillation,notably hydrocarbon cuts distillation. In this application, the packingaccording to the invention is arranged in a column provided with atleast one feed line and two withdrawal lines for a heavy phase and alight phase.

1. A structured packing of a fluid contacting column defining anexchange surface for at least one liquid phase intended to come intointimate contact with at least one gas phase, said packing consisting ofa pile of plates comprising corrugations, each plate being inscribedbetween two parallel planes, said corrugations forming a succession ofpositive and negative edges, each edge comprising fins inscribed betweensaid two parallel planes, each one of said fins consisting of at leastone band cut out in one of said plates, width of the band rangingbetween 1 and 15 mm, the band remaining secured to the plate on at leastone side and the band being deformed so as to create an orifice forminga discontinuity on the surface of the plate, wherein direction of theedges of a plate forms a non-zero angle with respect to direction of theedges of an adjacent plate, characterized in that each plate comprisesat least one longitudinal zone parallel to one lip of the plate, wherethe edges comprise no orifice, said zones being positioned in such a waythat two adjacent plates have their said zone one above the other so asto form at least one point of contact between a positive edge and anegative edge of two adjacent plates.
 2. A packing as claimed in claim1, wherein each plate comprises at least one zone at the centre of theplate and/or on the periphery of the plate.
 3. A packing as claimed inclaim 2, wherein each plate comprises a zone at the centre of the plateand a zone close to the lip.
 4. A packing as claimed in claim 1, whereineach longitudinal zone extends over the entire length of the lip of theplate it is parallel to.
 5. A packing as claimed in claim 1, wherein thewidth of a longitudinal zone is greater than or equal to width of thebands of the fins.
 6. A fluid contacting column comprising severalblocks with structured packings as claimed in claim 1, wherein saiddirection of the packing channels is oriented at an angle rangingbetween 10° and 75° with respect to the axis of the column and where themedian planes of the structured packing of one of said blocks form anangle ranging between 20° and 90° with respect to the median planes ofthe adjacent blocks.
 7. Application of a contacting column as claimed inclaim 6 for gas drying, natural gas deacidizing, fumes decarbonation,Claus tail gas treatment or distillation.